They were supposed to join Australia’s HMAS Adelaide — a similar ship with a similar purpose — in practising assaults on defended islands during the recent enormous RIMPAC 2018 war games off Hawaii.

It’s a relevant scenario.

China has, after all, just arbitrarily claimed most of the South and East China Seas, built artificial islands — and heavily fortified them.

But, for RIMPAC, Australia, the Philippines and were left to carry the weight for friendly forces.

A landing craft, air cushion assigned to Assault Craft Unit (ACU) 5 launches from the well deck of the amphibious assault ship USS Bonhomme Richard (LHD 6), tied up at Pearl Harbor with engine problems during Rim of the Pacific (RIMPAC). Picture: US NavySource:Supplied

UNDER PRESSURE

America’s USS Bonhomme Richard (LHD-6) spent half the war games tied up alongside a pier in Pearl Harbor. The USS Boxer (LHD-4) never arrived.

On board was the commander for RIMPAC’s naval task groups, Chilean Navy Commodore Pablo Niemann Figari. He was forced to command the fleet from shore.

USS Bonhomme Richard was commissioned in 1998. It can carry 1800 troops, six Harriers, four attack helicopters, 12 Osprey tilt-rotors and four Super Stallion heavy-lift helicopters.

Some of these troops and helicopters diverted to HMAS Adelaide to participate in the practice beach assault.

Assault amphibious vehicles transport Marines from multiple partner nation ships during the amphibious demonstration as part of the Rim of the Pacific (RIMPAC) exercise. Picture: US NavySource:Supplied

USS Boxer was commissioned in 1995. It’s built to the same design as USS Bonhomme Richard - carrying fighters, Ospreys, helicopters and landing craft to deploy its cargo of troops.

It also had mechanical issues, but this time before RIMPAC got underway.

“There was going to be some more amphibious operations. One of the ships we had identified had some mechanical issues, so we were not able to get her out of maintenance in time to do that. … Most of the amphibious operations turned into land training with our partner nations and our Marines there at (California’s Camp) Pendleton,” 3rd Fleet commander Vice Admiral John Alexander said.

Commanding Officer 2nd Battalion (Amphibious), Royal Australian Regiment, Australian Army officer, Lieutenant Colonel Doug Pashley, addresses soldiers and marines from Australia, Japan, Malaysia, Sri Lanka, the United States and Tonga onboard HMAS Adelaide during Exercise Rim of the Pacific 18, Hawaii. Picture: DefenceSource:Supplied

AUSTRALIA TAKES THE STRAIN

The United States isn’t the only nation to have amphibious assault ships.

Australia recently acquired two: HMAS Adelaide and Canberra.

HMAS Adelaide was taking part in RIMPAC. It was supposed to operate in the troop deployment and helicopter support role alongside USS Bonhomme Richard and USS Boxer.

It ended up operating almost alone. The Philippines helped take up the troop transport slack with their new landing ship (dock) BRP Davao del Sur.

A United States Marine Corps Amphibious Assault Vehicle hits the beach at Kaneohe Bay after disembarking HMAS Adelaide during the final amphibious assault for Exercise RIMPAC 2018. Piture: DefenceSource:Supplied

HMAS Adelaide is based on a Spanish design. It can carry between 1046 and 1600 troops, up to 110 vehicles and eight helicopters. It also has a ski-jump to support visiting Harrier and F-35B jump jets.

The beach landing was considered the main event of RIMPAC. This part alone involved seven nations and 300 troops. Five waves of amphibious assault vehicles stormed the shore, supported by helicopters and gunships.

HMAS Adelaide was at the heart of it all.

Royal Australian Navy landing craft and United States Marine Corps Amphibious Assault Vehicles move from HMAS Adelaide toward Bellows Beach in Hawaii to conduct the final amphibious assault for Exercise RIMPAC 18. Picture: DefenceSource:Supplied

From her decks flew a multinational force of helicopters — both gunships and troop transports.

From her dock departed armoured US Marine amphibious fighting vehicles, as well as troops from a variety of nations aboard landing craft.

Her command-and-control rooms took up the strain of co-ordinating the attack.

In the thick of it all was HMAS Adelaide’s MRH-90 helicopters.

“On any given day we’re flying for a range of purposes, from something as simple as providing transport for personnel between other ships and ashore, to supporting multinational amphibious forces securing a beach with assault vehicles and landing craft,” pilot Lieutenant Ryan Cross said.

A United States Marine Corps AH-1Z Viper attack helicopter takes off as two Marine Corps UH-1Y Venom transport helicopters prepare to launch from HMAS Adelaide's flight deck during a multi-spot exercise. Picture: DefenceSource:Supplied

HMAS Adelaide’s Commanding Officer Captain Jonathan Earley said the ship’s helicopters had displayed a sustained level of operations never before seen on the LHD.

“A Landing Helicopter Dock carries a significant capability when it deploys on tasks over the horizon and, for HMAS Adelaide, a huge part of that capability depends on the efforts of the 37 personnel flying and maintaining the aircraft.”

Now, the assault is over. The beachhead has been secured. Protected by an international flotilla of warships and submarines, HMAS Adelaide is headed back to base.

Soldiers from the 2nd Battalion, Royal Australian Regiment and United States Marines during the amphibious assault. HMAS Adelaide is on the horizon. Picture: DefenceSource:Supplied

EXCESSIVE DEMAND

When it comes to amphibious assault ships, the US military has a supply-and-demand problem.

They’re just too useful.

For disaster relief, their helicopters, medical facilities and carrying capacity are lifesavers.

For showing the flag, their size and array of aircraft are impressive.

For war games, their role is both central and exceptionally relevant.

A US Government chart detailing the decline in numbers of amphibious assault ships in the US Navy. In the background is USS Bonhomme Richard. Picture: US NavySource:Supplied

The United States Navy has 31 ships in the amphibious category, ranging from the aircraft carrier-like Bonhomme Richard to smaller vessels intended to carry tanks to the shore.

Last year, the US Government Accountability Office ruled that this was not enough to maintain training standards for the US Marines as well as maintain active Amphibious Ready Groups and Marine Expeditionary Units.

Something had to give.

The ships are working double-time. And their crews and troops are not getting the training they need.

A landingcraft assigned to the Royal Australian Navy landing helicopter dock ship HMAS Adelaide (L01), as part of AAV operation training during the Rim of the Pacific (RIMPAC) exercise. Picture: US NavySource:Supplied

* The original version of this story incorrectly reported the USS Portland (LPD-27) had broken down and was unable to participate in RIMPAC. While the ship was in Hawaii, it served as the 3rd Fleet Ship for the duration of the exercise. Its identity was confused with the USS Boxer (LHD-4).